Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our
fascinating universe is featured, along with a brief explanation
written by a professional astronomer.

2025 November 20

Alnitak, Alnilam, Mintaka
Image Credit & Copyright: Aygen Erkaslan

Explanation: Alnitak, Alnilam, and Mintaka are the bright bluish stars
from east to west (upper right to lower left) along the diagonal in
this cosmic vista. Otherwise known as the Belt of Orion, these three
blue supergiant stars are hotter and much more massive than the Sun.
They lie from 700 to 2,000 light-years away, born of Orion's
well-studied interstellar clouds. In fact, clouds of gas and dust
adrift in this region have some surprisingly familiar shapes, including
the dark Horsehead Nebula and Flame Nebula near Alnitak at the upper
right. The famous Orion Nebula itself is off the right edge of this
colorful starfield. The telescopic frame spans almost 4 degrees on the
sky.

Tomorrow's picture: interstellar
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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Amber Straughn Specific rights apply.
NASA Web Privacy, Accessibility, Notices;
A service of: ASD at NASA / GSFC,
NASA Science Activation
& Michigan Tech. U.

--- BBBS/Li6 v4.10 Toy-7
* Origin: The Rusty MailBox - Penticton, BC Canada (1:153/757)

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our
fascinating universe is featured, along with a brief explanation
written by a professional astronomer.

2025 November 21

3I/ATLAS: A View from Planet Earth
Image Credit & Copyright: Rolando Ligustri

Explanation: Now outbound after its perihelion or closest approach to
the Sun on October 29, Comet 3I/ATLAS is only the third known
interstellar object to pass through our fair Solar System. Its greenish
coma and faint tails are seen against a background of stars in the
constellation Virgo in this view from planet Earth, recorded with a
small telescope on November 14. But this interstellar interloper is the
subject of an on-going, unprecedented Solar System-wide observing
campaign involving spacecraft and space telescopes from Earth orbit to
the surface of Mars and beyond. And while the comet from another
star-system has recently grown brighter, you'll still need a telescope
if you want to see 3I/ATLAS from planet Earth. It's now above the
horizon in November morning skies and will make its closest approach to
Earth, a comfortable 270 million kilometers distant, around December
19.

Tomorrow's picture: Dione and Rhea Ring Transit
__________________________________________________________________

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Amber Straughn Specific rights apply.
NASA Web Privacy, Accessibility, Notices;
A service of: ASD at NASA / GSFC,
NASA Science Activation
& Michigan Tech. U.

--- BBBS/Li6 v4.10 Toy-7
* Origin: The Rusty MailBox - Penticton, BC Canada (1:153/757)

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our
fascinating universe is featured, along with a brief explanation
written by a professional astronomer.

2025 November 22

Dione and Rhea Ring Transit
Image Credit & Copyright: Christopher Go

Explanation: Seen to the left of Saturn's banded planetary disk, small
icy moons Dione and Rhea are caught passing in front of the gas giant's
extensive ring system in this sharp telescopic snapshot. The remarkable
image was recorded on November 20, when Saturn's rings were nearly
edge-on when viewed from planet Earth. In fact, every 13 to 16 years
the view from planet Earth aligns with Saturn's ring plane to produce a
series of ring plane crossings. During a ring plane crossing, the
interplanetary edge-on perspective makes the thin but otherwise bright
rings seem to disappear. By November 23rd Saturn's rings will have
reached a minimum angle for now, at their narrowest for viewing from
planet Earth, but then start to widen again. Of course, Dione and Rhea
orbit Saturn near the ring plane once every 2.7 and 4.5 days
respectively, while the next series of Saturn ring plane crossings as
seen from Earth will begin again in 2038.

Tomorrow's picture: everything, everywhere, all at once
__________________________________________________________________

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Amber Straughn Specific rights apply.
NASA Web Privacy, Accessibility, Notices;
A service of: ASD at NASA / GSFC,
NASA Science Activation
& Michigan Tech. U.

--- BBBS/Li6 v4.10 Toy-7
* Origin: The Rusty MailBox - Penticton, BC Canada (1:153/757)

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our
fascinating universe is featured, along with a brief explanation
written by a professional astronomer.

2025 November 23
A diagram is shown depicting various parts of the universe that are
observable. In the middle are the parts closest to Earth, and around
the far edges are parts furthest from Earth. Planets, galaxies, and the
CMB are illustrated. Please see the explanation for more detailed
information.

The Observable Universe
Illustration Credit & Licence: Wikipedia, Pablo Carlos Budassi

Explanation: How far can you see? Everything you can see, and
everything you could possibly see, right now, assuming your eyes could
detect all types of radiations around you -- is the observable
universe. In light, the farthest we can see comes from the cosmic
microwave background, a time 13.8 billion years ago when the universe
was opaque like thick fog. Some neutrinos and gravitational waves that
surround us come from even farther out, but humanity does not yet have
the technology to detect them. The featured image illustrates the
observable universe on an increasingly compact scale, with the Earth
and Sun at the center surrounded by our Solar System, nearby stars,
nearby galaxies, distant galaxies, filaments of early matter, and the
cosmic microwave background. Cosmologists typically assume that our
observable universe is just the nearby part of a greater entity known
as "the universe" where the same physics applies. However, there are
several lines of popular but speculative reasoning that assert that
even our universe is part of a greater multiverse where either
different physical constants occur, different physical laws apply,
higher dimensions operate, or slightly different-by-chance versions of
our standard universe exist.

Explore the Observable Universe: Random APOD Generator
Tomorrow's picture: stellar shell game
__________________________________________________________________

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Amber Straughn Specific rights apply.
NASA Web Privacy, Accessibility, Notices;
A service of: ASD at NASA / GSFC,
NASA Science Activation
& Michigan Tech. U.

--- BBBS/Li6 v4.10 Toy-7
* Origin: The Rusty MailBox - Penticton, BC Canada (1:153/757)