Planet Venus High in the Sky

 
On January 10, 2025, Venus will reach its Greatest Eastern Elongation. Venus, the brightest "star" in the evening western skies, outshines everything else. Just after sunset, in the evening twilight, it is easy to spot this diamond in the sky.

Greatest Elongation refers to the largest angle formed between Earth, the Sun, and a planet—in this case, Venus. On this day, Venus will appear 47 degrees away from the Sun as seen from Earth. As both Earth and Venus orbit the Sun, the angle between Venus and the Sun (as viewed from Earth) changes. When the planets align with Venus between Earth and the Sun, the angle is zero, an event known as Inferior Conjunction. Since Venus orbits closer to the Sun and moves faster than Earth, this angle increases, eventually reaching a maximum of 47 degrees. After this point, the angle begins to decrease until it reaches zero again. When Venus aligns on the far side of the Sun relative to Earth, this is called a Superior Conjunction.

At Greatest Eastern Elongation, Venus will display a nearly half-phase and will set late in the evening. As the days pass, the angle between the Sun and Venus will gradually reduce, but Venus's apparent size will increase. The phase will change from half to a crescent as the distance between Venus and Earth decreases.

At Greatest Elongation, Venus's angular size will be 24.6 arcseconds, with the planet located 101,742,566 km from Earth. As Venus continues to approach Earth, its angular size will increase to 46 arcseconds by the end of February, while its distance decreases to 53,967,713 km. Venus will be closest to Earth on March 22, 2025, at a distance of 41,977,162 km, just before reaching Inferior Conjunction on March 23, 2025.

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Sun as Blind(Bright) Spot

 

Blind Spot, something we are all familiar with and have experienced it one time or the other. With all the mirrors around in the car or truck there will be one area where we cannot see and we have to adapt and work around it. Sometimes its a matter of life and death. Something which we cannot observe even with mirrors, this got me thinking of astronomers and their mirrors, the telescope and blind spot ,that area where observation is not possible. Earth rotates on its axis every 24 hours and if a solar eclipse is happening in USA, we in India will be at the opposite side with nightfall, but at-least someone got to see the eclipse. But there are places in the sky where if some events happen nowhere on earth can we see or observe the event. This is the portion of the sky where the Sun is placed.

On a new moon day we cannot the see the moon, it's not that moon has vanished from the sky but its hidden in the glare of the Sun. When a celestial object is close to the Sun we call that object as, in conjunction with Sun. During new moon phase the moon is in conjunction with the Sun. This applies to planets too, planets Jupiter and Saturn were in conjunction with Sun in late January of this year and as you know by now, conjunction means close to the Sun. When planets are in conjunction with the Sun observations cannot happen and we have to wait for the planets to come out of Sun's glare. This can take from several days to months and during that time there is nothing that the earth bound astronomers can do but wait.

The dreaded wait, how many of you reading this article remember the wait for the emergence of COMET ISON in 2013. The COMET ISON was dubbed to be the comet of the century and was to be the brightest comet in the sky after its perihelion (close approach to Sun). The comet was observed and followed until it fell into the glare of the Sun, amateurs and professional astronomers waiting to see the reappearance never got the chance as the comet got disintegrated during its close approach to Sun. We had wonderful images before it went close to Sun, but as it got close to Sun all we could do was to wait for emergence as sun's glare hid the comet.

If we go back in time to 1994 and the event of great impact of comet Shoemaker Levy 9 on to the planet Jupiter, which proved Eugene Shoemaker's theory of the impacts by comets and asteroids on Planets are common, well in astronomical timeline of-course. The event took place in July and telescopes around the world were pointing at Jupiter and astronomers studied the event in great detail. At that time Jupiter was in the constellation of Virgo and the Sun was in the constellation of Gemini. Imagine if the same event would have taken place during conjunction of Jupiter with Sun, we would have missed the great event.

Its not only planets but stars and other celestial objects too that come close to the Sun in the sky during the year, reaching conjunction, and those objects also cannot be observed until they emerge out of the glare. For example ,in the month of February Sun is in the constellation of Capricornus and we cannot see the stars or the objects in the constellation due to the bright Sun.

In the month of January of 2020 the red star in Orion constellation, Betelgeuse, dimmed in brightness unexpectedly and astronomers were able to measure the brightness until it came back to its original brightness in April of 2020. This was a good opportunity to study the brightness variation of the star as Betelgeuse was well placed in the sky away from the bright Sun. The same event if it had happened in the month of June, you know where I am going with this, yes Betelgeuse will be in conjunction with Sun in June.

There are many such rare events that we could have missed if the event had taken place during conjunction with Sun, even the closest supernova in Large Magellanic Cloud which took place in 1987 if it had happened during conjunction.

Sun is a big blind spot for astronomers, even with their mirrors they will miss anything close to Sun. Astronomers take advantage of even the smallest window and try to learn everything they can, because they know that these are rare events. For astronomers there is no such thing as being at right time at right place, they have to make best of what they get.

Knowing this I am very sure that it will make us look at each event and night as a gift and accept it with a sense of gratitude.

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Sun Farthest from Earth

Sun is far away and still its hot summer in the northern hemisphere. This is the question many have, relating to the distance to the Sun and seasons on earth. The seasons on earth is due to the tilt of the earth at 23.5 degrees. Due to this tilt northern and southern hemispheres are exposed to the Sun during certain months of the year. While Northern hemisphere is exposed to more sun during March to September, the Southern hemisphere will be going through winter and situation reverses after September. From September to March Southern hemisphere is exposed to more Sun and it will be Summer in southern hemisphere while northern hemisphere will be experiencing winter. This is how seasons change on earth.

Earth Tilt and Seasons Credit:CC

Earth makes one full revolution of the Sun in approx 365.256 days. In this orbit around the Sun there are two points where the Sun and earth are closest, called Perihelion, and the other point is the farthest distance between Sun and earth and this point is called Aphelion. The two points Perihelion and Aphelion exists because the orbit of earth around the Sun is not a circular one, it orbits in an elliptical orbit but the difference is very small at an eccentricity of 0.0167. This small elliptical orbit makes the earth”s perihelion distance close to 147 million kilometres and aphelion distance close to 152 million kilometres.

Earth elliptical orbit Perihelion and Aphelion  Credit: ABAA

Earth reaches perihelion on January 5^th and aphelion on July 4^th. During Perihelion the Sun is in the constellation of Sagittarius and earth will be moving around the Sun at a velocity of 1,08,900km/h and has an angular diameter of 32m32s of arc. During Aphelion on July 4^th Sun will be in the constellation of Gemini and earth will be moving around the Sun at a velocity of 1,07,208km/h and will have angular diameter of 31m28s of arc.

Sun Angular size at Aphelion and Perihelion  Credit: ABAA

Happy Observing and Clear Skies.

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Earth and Sun Closest

Sun so close yet so cold...Yes Today Sun and earth will be closest to each other at a distance of 14,70,99,586 km. This point of any object closest to Sun is called Perihelion. The reason for the cold in northern hemisphere is due to the orientation of earth's axis and as you can see in the illustration, the Sun is moved to southern hemisphere where they are experiencing Summer now. 

Since earth's orbit is almost circular, at farthest point from Sun which occurs on July 6th the distance will be 15,20,96,155 km. This farthest point from Sun is called Aphelion. The angular size of the Sun which we measure in degrees at perihelion is 0.542018074degrees. And as we know the orbit is almost circular the difference in angular diameter of Sun from Perihelion to Aphelion is very small. At Aphelion the angular diameter is 0.5243709741degrees. 

 If we compare this to Mercury, the perihelion distance is 46,000,000 and this gives the angular diameter of Sun Seen from Mercury at 1.73434325degrees. The Aphelion distance of Mercury is 69,820,000 and this gives the angular diameter of Sun as seen from Mercury at 1.14247784degrees, almost half a degree difference. You can compare this to earth and Sun.

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Earth at Perihelion:

Earth will be at Perihelion on 4^th of January; this is the closest distance from earth to Sun. At perihelion the distance between earth and sun is close to 147.09 million km. Since Earth’s orbit eccentricity is very low at 0.016 which is very close to circle the distance between perihelion and aphelion (furthest point from Sun) does not differ much. The Aphelion distance of earth and Sun is 152.10 million km, making the difference just 5.01 million kilometres. This is not much to cause any problem to us, but due to proximity to sun earth receives 7% more sunlight.

The angular size of the Sun seen from earth does not differ much during perihelion and aphelion due to low eccentricity for earth’s orbit. The sun subtends an angle of 0.54183 degrees during perihelion, and at aphelion (furthest distance from sun) the angle subtended is 0.52398 degrees the difference is very small at 0.01785 degrees.

When compared with Mercury which has highest eccentricity of 0.2056 the difference in angular size is apparent during perihelion and aphelion.

 

		Sun			Sun
		Max.Angular Dia			Min.Angular Dia
		Perihelion			Aphelion
Earth		0.54183			0.52398
Mercury		1.7324			1.1414

 

Say Hi to Sun when you go out on January 4^th!

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Sun's Angualr size as seen from different planetary distances

When we look at the sun, we always wonder how big it would appear looking at it from different planets. I have made this Image to show the relative size of Sun as seen from different planetary distances (scroll down after the table). The angular size of Sun with respect to distance is easy to calculate. Divide diameter of Sun by its distance form earth and then multiply the result by 57.3 to get the angular size of sun. Using this we can get angular size of Sun from different planets...

Angular size = diameter/distance * 57.3

Diameter of Sun = 1391000km

Distance from Earth = 150000000km

Angular size = 1391000/150000000

= 0.0092 * 57.3

Angular size of Sun as seen from earth = 0.531degrees.

We can calculate and compare the relative angular size of Sun seen from different planetary distances.

Sun Diameter = 1391000 kilometers
Planets	Distance from Sun  (when planet is closest to sun)	Angular diameter(in degrees)
Mercury	46000000	1.73
Venus	107000000	0.74
Earth	150000000 (mean distance)	0.53
Mars	206000000	0.38
Jupiter	740000000	0.10
Saturn	1352000000	0.05
Uranus	2741000000	0.029
Neptune	4444000000	0.017

Here is the a graphic of sun's appearance at different distances...

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Last Venus Transit of the Century

We have waited 8 years for this event on June 6^th this year and if we miss it, its just another 105 years wait for this event to re occur. This event is Transit of Venus, and the last time we observed was on June 8^th 2004 and its going to take place again on June 6^th this year. In 2004 we could see both Ingress, that is Planet entering Sun's disc, and also Egress meaning Planet coming out of Sun's disc. Many had luck observing the full event but a lot of us had to deal with clouds, as monsoon was just starting.

Since March 26^th 2012 after the Greatest Elongation of Venus, we are observing the planet slowly shrinking in altitude in the evening sky and also observing the changing phases of Venus through the telescope, Venus changing from Half lit to Crescent phase and also we have been noticing that the  planet is  getting bigger in angular size and with this we can conclude that Venus is coming closer and in a few days time it will be between the Earth and the Sun.

When Venus comes between Earth and the Sun, the planet is said to be in Inferior Conjunction. On June 6^th Venus will be in Inferior Conjunction, this day also happens to be when Venus and Earth lie in the same orbital plane making Sun, Venus and Earth lie in an exact line. When this happens, we can see Venus moving across the Sun's disc, This is called Transit of Venus.

Why  Venus transit does not happen on all Inferior Conjunctions? This is because, Venus's orbital plane is inclined at an angle of 3.39 degrees and only when Venus and Earth line up exactly in this  plane, we can see a transit. The alignment of Earth orbit meeting the Venus orbit happens in the month of June and December, during this time when the planet aligns exactly in line we see a transit. Venus Transits reoccur at intervals of 8, 121.5, 8 and 105.5 years, last was in 2004 and now in 2012, we are going to see it again in 2117 and 2125 both in December.

For our region Venus Transit on 6^th June starts at 3:40am so we have to wait till sunrise to see the transit. It would be a wonderful sight to watch sunrise with Venus as a black circular dot in the north on Sun's disc.

Sun Rise at 5:52am

Transit starts	03:40:00 AM
Minimum separation	07:00:00 AM	Sun Altitude 14degrees 30minutes
Transit Ends	10:20:00 AM	Sun Altitude 60degrees 18minutes

Make sure you are in an area where you have clear horizon and its not blocked by buildings and trees. Never look at the sun directly, the best way to observe the sun is through the sun filters.

Ways of observing the event :

NEVER LOOK AT THE SUN DIRECTLY, ALWAYS USE PROPER FILTERS.

Viewing with the help of Binocular:

If you have a pair of binoculars you can fix the binocular on to a stand and project the image of the Sun on to a cardboard or wall and safely watch the Transit. Do not point the binoculars at the sun for long duration at a time. Again NEVER LOOK AT THE SUN DIRECTLY THROUGH THE BINOCULAR use binoculars only to project the image.

Observing with help of telescope:

If you have a telescope, you can use the telescope to project the image of the sun on to a wall or a screen. Before doing that it is advisable to make a mask with small opening that is smaller than the mirror size, like the one shown in the photo and attach it in front of the tube to reduce intensity of the sun and also this will help in increasing the contrast of the image.

This is called an off axis mask.

NEVER LOOK THROUGH THE TELESCOPE AT THE SUN, THIS WILL DAMAGE YOUR EYES PERMANENTLY.

After attaching the mask you can use the telescope to project the image and observe it safely. 

Every few minutes move the telescope away from the sun so that the heat of the sun does not damage the optical system.

Buy a proper solar filter to observe the sun, do not use sun glasses to see the sun.

Cassegrain telescopes should not be used to project sun, as the internal heat can damage the optical system. 

You can visit transitofvenus.org website for further information on observing advice.

Hope you all have a wonderful observing session this June 6th. Make sure you spread the word and educate people about the Transit.

All the best and Clear skies.

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Sun closest to Earth on January 5th

On January 5^th the earth will be closest to the Sun. During its orbit around the Sun, the earth does not follow a circular path, it deviates a little with an eccentricity 0.0167. This deviation is very small making the distance of earth-sun during the perihelion and aphelion very small. The difference will be close to 3 percent. Perihelion is when a celestial body is closest to the Sun and Aphelion is when the celestial body is farthest from Sun.

On January 5^th earth will be at a perihelion distance of 147 million (Km) and at this distance the Sun's angular diameter will be 32.5 minutes of arc. The orbital velocity of earth during the perihelion will be close to 109044 km/hr.

We can compare this with Aphelion distance of earth, the maximum distance 152 million (Km). The angular diameter at this maximum distance will be 31.45 minutes of arc. The orbital velocity at this distance will be 105444 km/hr.

Earth will be at Aphelion on 5^th July this year.

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Planets for the Month

Mercury:

Mercury will reach inferior conjunction on September 3^rd. It will be lost in the Sun's glare in the first week of September. During second week, Mercury will be too close to eastern horizon at around 8 degrees at 6am. After 15^th the planet Mercury will be little easy to spot if there is a clear horizon. Mercury will reach greatest elongation on 19^th September, the angular separation from the Sun will be 18degrees. Mercury will be in the constellation of Leo all month.

Date	Rise
1st Sep	06:35:00 AM
8th Sep	05:35:00 AM
15th Sep	05:02:00 AM
22nd Sep	04:59:00 AM
29th Sep	05:15:00 AM

Venus:

Venus will continue to dominate the evening western sky all this month. On 11^th September, Venus and crescent Moon will be close to each other at a separation of just 1 degree.

Date	Set
1st Sep	08:53:00 PM
8th Sep	08:43:00 PM
15th Sep	08:31:00 PM
22nd Sep	08:16:00 PM
29th Sep	07:57:00 PM

Venus and Mars

Mars:

The red planet will be in the constellation of Virgo all month. Mars can be spotted in the western sky evening sky 6 degrees north of Venus.

Date	Set
1st Sep	08:50:00 PM
8th Sep	08:38:00 PM
15th Sep	08:26:00 PM
22nd Sep	08:15:00 PM
29th Sep	08:04:00 PM

Jupiter:

Jupiter is well placed for observations as it rises early in the evening. The giant planet will the brightest “star” in the region at -2.5 magnitude.

On 19^th September, Jupiter and Uranus will be close each other at an angular separation of 48 minutes of arc. An 8 inch f/8 telescope with 32mm eyepiece will show the giant planet and Uranus in single field.

Jupiter will reach opposition on September 21^st , this means, the planet Jupiter, Earth and the Sun will be the straight line. As a result, Jupiter will rise as the Sun sets, giving observers chance to study the planet all night.

Date	Rise
1st Sep	07:41:39 PM
8th Sep	07:11:24 PM
15th Sep	06:40:56 PM
22nd Sep	06:10:22 PM
29th Sep	05:39:48 PM

Field in binocular

Saturn:

Saturn, now low in the western horizon is getting difficult to spot. In the constellation of Virgo, the planet Saturn will be lost in the Sun's glare towards the end of the month.

Date	Set
1st Sep	07:58:32 PM
8th Sep	07:33:42 PM
15th Sep	07:08:56 PM
22nd Sep	06:44:14 PM
29th Sep	06:19:33 PM

Uranus:

Uranus can be easily be seen through a 10X50 binoculars. Now its easier as Jupiter can be taken as reference. Pick up the binoculars and point it towards Jupiter and keep the Jupiter at the center of field. Just 1 degrees west to Jupiter you will find 5.7^th magnitude Uranus.

Uranus will also reaches opposition on 21^st of September, same day as Jupiter.

Date	Rise
1st Sep	07:34:44 PM
8th Sep	07:06:20 PM
22nd Sep	06:09:28 PM
29th Sep	05:41:02 PM

Neptune:

Neptune will be in the constellation of Capricornus in the month of August. Planet Neptune can be found at 4 degrees NE of delta Capricorni. Neptune is at magnitude of 7.8. Neptune will be just 1 degree NE of mu Capricorni

Date	Rise
1st Sep	05:44:39 PM
8th Sep	05:16:30 PM
15th Sep	04:48:22 PM
22nd Sep	04:20:17 PM
29th Sep	03:52:15 PM

Pluto:

Pluto still is in the rich star field of constellation Sagittarius at 14^th Magnitude.

Phases of Moon:

New moon: 08 Sep 2010

First quarter: 15 Sep 2010

Full moon: 23 Sep 2010

Last quarter: 01 Oct 2010

Sun:

Sun will be in the constellation of Leo till middle of September and move to Virgo.

Equinox:

On 23^rd September at approximately 8:40am the Sun reaches RA of 12h and Dec of 0 degress, this is Autumnal Equinox. This point is also called as First point of Libra.

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Astronomy News

Amazing New Sun Images From NJIT’s Big Bear Solar Observatory

NJIT Distinguished Professor Philip R. Goode and the Big Bear Solar Observatory (BBSO) team have achieved “first light” using a deformable mirror in what is called adaptive optics at Big Bear Solar Observatory. The image was published today on the website of Ciel et l'Espace, as the photo of the day. In September, Ciel et l’Espace, a popular astronomy magazine, will publish several more photos of the Sun taken with BBSO’s new adaptive optics system.

Goode said that the images were achieved with the 1.6 m clear aperture, off-axis New Solar Telescope (NST) at BBSO. The telescope has a resolution covering about 50 miles on the Sun’s surface.

The telescope is the crown jewel of BBSO, the first facility-class solar observatory built in more than a generation in the U.S. The instrument is undergoing commissioning at BBSO. Since 1997, under Goode’s direction, NJIT has owned and operated BBSO, located in a clear mountain lake.

The mountain lake is characterized by sustained atmospheric stability, which is essential for BBSO’s primary interests of measuring and understanding solar complex phenomena utilizing dedicated telescopes and instruments.

The images were taken by the NST with atmospheric distortion corrected by its 97 actuator deformable mirror. By the summer of 2011, in collaboration with the National Solar Observatory, BBSO will have upgraded the current adaptive optics system to one utilizing a 349 actuator deformable mirror.

Summer of 2009, with support from the National Science Foundation (NSF), Air Force Office of Scientific Research, NASA and NJIT, the NST began operation. Additional support from NSF was received a few months ago to fund further upgrades to this new optical system.

The NST will be the pathfinder for an even larger ground-based telescope, the Advanced Technology Solar Telescope (ATST), to be built over the next decade. NJIT is an ATST co-principal investigator on this NSF project. The new grant will allow Goode and partners from the National Solar Observatory (NSO) to develop a new and more sophisticated kind of adaptive optics, known as multi-conjugate adaptive optics (MCAO). The new optical system will allow the researchers to increase the distortion-free field of view to allow for better ways to study these larger and puzzling areas of the Sun. MCAO on the NST will be a pathfinder for the optical system of NSO’s 4-meter aperture ATST coming later in the decade.

Scientists believe magnetic structures, like sunspots hold an important key to understanding space weather. Space weather, which originates in the Sun, can have dire consequences on Earth's climate and environment. A bad storm can disrupt power grids and communication, destroy satellites and even expose airline pilots, crew and passengers to radiation.

The new telescope now feeds a high-order adaptive optics system, which in turn feeds the next generation of technologies for measuring magnetic fields and dynamic events using visible and infrared light. A parallel computer system for real-time image enhancement highlights it.

Goode and BBSO scientists have studied solar magnetic fields for many years. They are expert at combining BBSO ground-based data with satellite data to determine dynamic properties of the solar magnetic fields.

source: NJIT

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