Stars and Constellations
In April, the spring sky is now prominent in the east, along with the familiar Big Dipper. The Big Dipper is high in the northeast, and the two stars at the end of the bowl can be used to find Polaris, our north star. Also, the handle can be used to "arc to Arcturus", a bright star in the constellation Boötes. Next, Leo the lion is very high in the east, approaching the middle of the sky now, with the constellation Virgo just below. The winter constellations are also visible, now in the west. Taurus the bull is getting lower in the west, near Orion the hunter to the west-southwest. Canis Major (the big dog), along with the bright star Sirius, is also getting low in the southwest. Gemini the twins is a little higher in the west, along with Auriga the charioteer in the west-northwest and Canis Minor (the little dog) in the southwest. The winter Milky Way is now getting lower in the west as well. Far to the south we can see some constellations making up part of Jason's Argo Navis, which we only get to see briefly since it is so far south. Finally, there is still a small portion of the fall sky still visible just for the first hour or so of the night. Cassiopeia the queen is in the north-northwest, and Perseus the hero is in the northwest.
In May, the winter constellations are lower in the west, and Orion, Taurus, and Canis Major are already in the process of setting at the beginning of the night, along with Cassiopeia and Perseus to the northwest. The spring constellations are higher now, and we can see the rest that weren't up this time last month. Hercules is below Boötes in the east-northeast. Some of the summer constellations are also getting ready to come up and will be visible a few hours after sunset.
Interesting Stars Visible in April and May (from 7-10 pm)
| Name / Designation | Apparent Magnitude (lower = brighter) | Distance (light-years) | Notes |
|---|---|---|---|
| Sirius | -1.44 | 8.6 | |
| Arcturus | -0.05 | 36.7 | |
| Vega | 0.03 | 25 | |
| Capella | 0.08 | 42 | |
| Rigel | 0.18 | 770 | |
| Procyon | 0.4 | 11 | |
| Betelgeuse | 0.45 | 427 | |
| Aldebaran | 0.87 | 65 | |
| Spica | 0.98 | 262 | |
| Pollux | 1.16 | 38 | |
| Regulus | 1.36 | 77 | means "Little King" |
| Castor | 1.58 | 52 | |
| Polaris | 1.97 | 431 | |
| Algol | 2.09 | 93 | variable star |
| Denebola | 2.14 | 36.2 | |
| Almak | 2.1 / 5.0 & 6.3 | 355 | triple star system w/ 64 yr orbit |
| Albireo | 3.2 / 5.8 & 5.1 | 390 / 380 | possibly a triple star system |
| Eta Cassiopeiae | 3.5 / 7.4 | 19 | 480 yr orbit |
Solar System
Mercury will become visible in the morning sky in early April, but in mid-May it will descend into the Sun's glare, eventually passing behind the Sun before the end of the month.
Venus is visible in the morning sky before sunrise, reaching its maximum height near the end of May.
Mars begins April nearly overhead after sunset, but gradually gets lower in the west each evening. It moves from Gemini, through Cancer, and into Leo.
Jupiter gets lower and lower in the west each evening, until it is barely visible by the end of May. It is in the constellation Taurus.
Saturn rises in the morning sky in early April just before sunrise, but gets a little higher each morning. It is in the constellation Pisces.
Jupiter Great Red Spot Transits in April and May (from 7-10 pm)
Note: The GRS is visible on the disk of Jupiter for 50 minutes before and after meridian transit time.
| DATE | MERIDIAN TRANSIT TIME |
|---|---|
| 04/01/25 | 07:24 PM |
| 04/03/25 | 09:03 PM |
| 04/08/25 | 08:13 PM |
| 04/10/25 | 09:52 PM |
| 04/13/25 | 07:23 PM |
| 04/15/25 | 09:03 PM |
| 04/20/25 | 08:13 PM |
| 04/25/25 | 07:23 PM |
| 04/27/25 | 09:02 PM |
| 05/02/25 | 08:12 PM |
| 05/07/25 | 07:23 PM |
| 05/14/25 | 08:12 PM |
| 05/19/25 | 07:22 PM |
| 05/31/25 | 07:22 PM |
Calendar of Night Sky Events
| Date | Event |
|---|---|
| 04/04/25 | First Quarter Moon. |
| 04/10/25 | Appulse of Mercury and Saturn — Separated by 2.0°. |
| 04/12/25 | Full Moon |
| 04/16/25 | Appulse of Mercury and Neptune — Separated by 0.7°. |
| 04/20/25 | Last Quarter Moon. |
| 04/21/25 | Mercury at greatest western elongation. — Visible in the morning sky. |
| 04/22/25 | Peak of Lyrids meteor shower. |
| 04/27/25 | New Moon. |
| 04/28/25 | Appulse of Venus and Saturn — Separated by 3.7°. |
| 05/03/25 | Appulse of Venus and Neptune — Separated by 2.0°. |
| 05/04/25 | First Quarter Moon. |
| 05/04/25 | Peak of Eta Aquariids meteor shower. |
| 05/12/25 | Full Moon. |
| 05/17/25 | Uranus at conjunction. — Passing behind the Sun. |
| 05/20/25 | Last Quarter Moon. |
| 05/24/25 | Appulse of Mercury and Uranus — Separated by 0.1°. |
| 05/26/25 | New Moon. |
| 05/29/25 | Mercury at superior conjunction. — Passing behind the Sun. |
| 05/31/25 | Venus at greatest western elongation. — Visible in the morning sky. |
Deep Sky
The winter Milky Way is now getting low in the west, but there are still several interesting objects we can see here. The Pleiades (Seven Sisters, M45) is close to the west-northwest horizon right next to the Hyades (C41), which makes the face of Taurus the bull. The constellation Auriga is a little bit higher, where we can see M36, M37, and M38, which are visible with binoculars. The Double Cluster (C14) in Perseus is low in the north-northwest. Higher in the sky we have the Beehive (Praesepe, M44) in Cancer the crab and Coma Berenices (Bernice's Hair) near the tail of Leo.
We are now beginning to see some globular clusters coming up in the east. M3 is towards the east, in the constellation Boötes. Nearby, the famous Hercules Globular (M13) is low to the east-northeast.
For nebulae, we have the spectacular Orion Nebula (M42) now now getting low to the west-southwest. This is the closest star-forming region to our solar system. We also have some good planetary nebulae, which come from dying stars. The Eskimo (C39) in Gemini is high in the west, the Owl (M97) in Ursa Major is high in the northeast, and the Ghost of Jupiter (C59) is to the south in the constellation Hydra.
And now the galaxies: In Ursa Major to the north we have Bode's Galaxy (M81) and the Cigar Galaxy (M82), close enough to be seen together in a low-power telescope. Nearby in the constellation Canes Venatici we have the Whirlpool (M51), which is a pair of colliding galaxies. The Pinwheel Galaxy (M101) is also nearby near the handle of the Big Dipper. Then the Sombrero Galaxy (M104) is in the southeast in the constellation Virgo.
Interesting Deep Sky Objects to Observe during April and May (from 7-10 pm)
| Designation | Name | Apparent Magnitude | Apparent Size | Distance (light-years) | Type |
|---|---|---|---|---|---|
| Messier 45 | Pleiades | 1.6 | 110' | 440 | open cluster |
| Messier 44 | Beehive Cluster | 3.7 | 95' | 577 | open cluster |
| Messier 42 | Orion Nebula | 4 | 85' x 60' | 1400-1600 | diffuse nebula |
| Messier 3 | (in Canes Venatici) | 6.2 | 18' | 34,000 | globular cluster |
| Messier 81 | Bode's Galaxy | 8.5 | 21' | 1,200,000 | spiral galaxy |
| NGC 3242 | Ghost of Jupiter | 8.6 | 25" | 1400 | planetary nebula |
| Messier 57 | Ring Nebula | 8.8 | 1' | 2,300 | planetary nebula |
| Messier 82 | Cigar Galaxy | 9.5 | 14' | 1,200,000 | galaxy |
Frequently Asked Questions
How big is our universe? Are there other universes?
This is a question that we may never be able to answer with certainty. But we can make some educated guesses that may either satisfy or fuel our curiosity.
First, we do have a limit to how far we can see in space. What we call the "observable" universe is defined by the speed of light and the age of the universe. To us this appears as a sphere with a radius of about 47 billion light years. (The reason this is not simply 13.8 billion light-years is because the universe is expanding.) Light from any objects farther than this distance has not yet had enough time to reach us.
The radius of the observable universe is steadily increasing at the speed of light, but because the expansion of our universe (not just the observable part) is accelerating, distant objects will eventually recede from us faster than the speed of light, making ever observing them impossible (barring any technological advances that might overcome this limit). Any objects currently beyond around 67 billion light years will never be within our observable universe.
Beyond the observable universe, we do not know if there is a physical boundary or any other kind of limits to space. People have estimated based on what we can see that if there is an edge to the universe, it must be at least 3.6 trillion light years away (80 times the observable limit). But it's also possible that our universe could be infinite, going on forever in every direction.
Thinking about other dimensions now, could other universes exist outside our own? By definition, we cannot observe or interact with anything outside our universe, so this question is left to philosophy or science fiction. Perhaps there was another universe before ours popped into existence. Or maybe (like Marvel's multiverse) there are many universes existing simultaneously. Interesting to ponder, but again, we may never know for sure.
If you have any questions you'd like me to answer in the next issue of SWG, please let me know. I'm also happy to take suggestions or comments, and also pictures if you'd like to send them. Happy viewing!
Date of publication: 2025