April 17, 2022
Sunday, April 17, 2022
Happy Easter! This is one of the latest Easters we've had because the first full moon after this year's spring equinox happened several weeks after the equinox, on April 16. More accurately, Easter happens on the first Sunday after the Paschal Full Moon which is usually the full moon after March 20 as based on observations from Jerusalem. Because our schools' spring breaks are tied to Easter, we're finishing up one of the latest spring breaks in a while.
This Thursday, on April 21 at 7:30 PM, the William M Thomas Planetarium will present “MARS One Thousand One”. While it's no longer required to be masked indoors at BC, with the vaccination rate at just 54% in Kern County, you may consider wearing a mask inside the closed space of the Planetarium, especially if you have or are living with someone with a compromised immune system. Doors open at 7 PM for general admission seating and are locked at 7:30 PM when the show begins. Go to the Planetarium's website at bakersfieldcollege.edu/community/planetarium for more information about the show.
Early risers tomorrow morning, April 18, will see four planets equally spaced in a line in the east-southeast. Jupiter will be at the far lower left, then Venus, then Mars and then finally Saturn at the upper right end. Jupiter and Venus will blaze brighter than any other star in the sky with Venus the brightest of all. Mars and Saturn will be as bright as the brighter stars in the sky. In the following mornings, you'll see Venus and Jupiter draw closer together. On April 27, a thin waning crescent moon will pass below the close pair. On April 30 Venus and Jupiter will be less than one moon diameter apart from each other (or about one pinky width at arm's length).
In a telescope you'll see Jupiter appearing the larger of the two as a full disk while Venus will appear as a gibbous, slightly more than half full. Over the coming months Venus will get smaller and more of its day side facing us as it moves farther away from us in its faster, inner orbit. Venus will be at superior conjunction, directly behind the sun as seen from Earth, on October 22.
In astronomy research news, we may be watching a Jupiter-size exoplanet being born in the young star system, AB Aurigae. The star is so young that it still has a disk of dust and gas swirling around it. There is a bright clump in the disk about three times farther out from the star than Neptune is from the sun. At such a distance from the star, it's possible to block the light from the star with a coronagraph and directly image the much fainter blob.
The light from the blob looks like it's from a protoplanet still glowing hot from formation. The reason this protoplanet is gaining so much attention is that it appears to be forming via a process called gravitational or disk instability instead of the usual expected process of core accretion where a forming planet builds up from small bits sticking together to make bigger and bigger things. If a protoplanet core gets big enough, it could then suck up a significant amount of the surrounding gas and quickly grow to Jupiter or Saturn size.
However, at such a large distance from the star, AB Aurigae, there shouldn't be enough disk material to form a giant planet so quickly through accretion. With the disk instability method, the outer parts of the disk may be cool and dense enough to collapse under its own gravity to make a protoplanet. If the blob is indeed a forming protoplanet, it would be the first good piece of evidence for the disk instability idea of planet formation along with the first forming planet that was directly imaged.
I've used tentative language to talk about the discovery because the blob has not been observed by other astronomy teams. The discovery team, led by Thayne Currie, used the 8.2-meter Suburu Telescope in Hawaii and the Hubble Space Telescope. It took quite a bit of data analysis and enhancement to pull out the blob from the rest of the material around the star. Maybe that data enhancement magnified a data artifact. Observers using the Very Large Telescope in Chile (four telescopes each with mirrors 8.2 meters across) and the Large Binocular Telescope in Arizona (uses two identical 8.4-meter telescopes mounted side-by-side) have not seen the blob and the ALMA observatory in the Atacama Desert sees just a smooth ring of dust in the sub-millimeter wavelength band instead of clumping. Confirmation of the blob needs to happen before we can really consider the possibility of a forming protoplanet.
I hope you'll be able to enjoy a truly dark sky filled with stars sometime this month!
—
Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com
