Jan 31

Sky Report: February 1 – February 7

Aldebaran to scale with our Sun. Mysid / Wikimedia Commons

The sole planet visible tonight in both the evening and morning sky is Mars, since all the others are behind the sun (or in front of it in the case of Mercury). But Mars is easy to see. At our southernly latitude it’s nearly overhead as darkness falls, and it’s the brightest “star” in that part of the sky. Mars is in Aries, one of the 13 constellations of the astronomical zodiac, and because Aries has no bright stars Mars stands out, being four times brighter than the brightest star of Aries.

There are three bright so-called “red” stars in the sky, although they’re orange to our eyes, and two of these three are to the east of Mars, which is also orange. Mars’ orange color comes from rusted minerals in the soil whereas the orange color of stars comes from their temperature — orange is cool. The closest of these two stars is Aldebaran, the eye of Taurus the Bull, and it lies 30°, or three times the width of your fist held at arm’s length, to the east of Mars. The other is Betelgeuse in Orion’s shoulder and it is two fist-widths continuing on in the same direction but a bit lower. Betelgeuse is precisely as bright as Mars and Aldebaran is a bit fainter. (The third bright red star is Antares in Scorpius.)

Aldebaran is an interesting star (actually they all are!). It’s a wonderful example of a “red giant” – an aged star that has swollen from its original size, which wasn’t much larger than our sun, to become 44 times our sun’s diameter and about 450 times as bright. Stars like our sun shine by converting hydrogen into helium in their interiors, but when a star ages the balance changes between the nuclear reactions in its core and the force of gravity, and the star expands enormously. The sun will do this in roughly 5 billion years.

Aldebaran is 65 light years distant, which means that the light we see tonight left Aldebaran in 1956. Surrounding it, but more distant, is a cluster of stars called the Hyades, and roughly half-way between Aldebaran and Mars is the smaller and prettier star cluster The Pleiades or Seven Sisters — and more on them in future Sky Reports.

Betelgeuse is also a red giant, but it is more distant and even larger.


The Sky Report is presented as a public service by the Stellar Vista Observatory, a nonprofit organization based in Kanab, Utah, which provides opportunities for people to observe, appreciate, and comprehend our starry night sky. Additional information is at www.stellarvistaobservatory.org. Send questions and comments to
John@StargazingAdventures.org.

About the Author:

John Mosley
John Mosley was Program Supervisor of the Griffith Observatory in Los Angeles for 27 years and is the author of “Stargazing for Beginners” and “Stargazing with Binoculars and Telescopes”. He and his wife live in St. George where he continues to stargaze from his retirement home while serving on the advisory committee for Stellar Vista Observatory.

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