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 September 28
Part of a large rock on Mars is shown being mostly orange. On the rock
are several irregular light-colored areas surrounded by a dark border.
The spots are only millimeters across but might be a remnant
biosignature of ancient Martian life. Please see the explanation for
more detailed information.

Leopard Spots on Martian Rocks
Image Credit: NASA, JPL-Caltech, MSSS, Perseverance Rover

Explanation: What is creating these unusual spots? Light-colored spots
on Martian rocks, each surrounded by a dark border, were discovered
last year by NASA's Perseverance Rover currently exploring Mars. Dubbed
leopard spots because of their seemingly similarity to markings on
famous Earth-bound predators, these curious patterns are being studied
with the possibility they were created by ancient Martian life. The
pictured spots measure only millimeters across and were discovered on a
larger rock named Cheyava Falls. The exciting but unproven speculation
is that long ago, microbes generated energy with chemical reactions
that turned rock from red to white while leaving a dark biosignature
ring, like some similarly appearing spots on Earth rocks. Although
other non-biological explanations have not been ruled out, speculation
focusing on this potential biological origin is causing much intrigue.

Tomorrow's picture: comet comet
__________________________________________________________________

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 September 29
A starfield is shown that has two short streaks running diagonally. At
closer inspection, they are two comets both with white-green heads and
white tails. Please see the explanation for more detailed information.

Two Camera Comets in One Sky
Image Credit & Copyright: Luc Perrot (TWAN)

Explanation: It may look like these comets are racing, but they are
not. Comets C/2025 K1 ATLAS (left) and C/2025 R2 SWAN (right) appeared
near each other by chance last week in the featured image taken from
France's Reunion Island in the southern Indian Ocean. Fainter Comet
ATLAS is approaching our Sun and will reach its closest approach in
early October when it is also expected to be its brightest -- although
still only likely visible with long exposures on a camera. The brighter
comet, nicknamed SWAN25B, is now headed away from our Sun, although its
closest approach to Earth is expected in mid-October, when optimistic
estimates have it becoming bright enough to see with the unaided eye.
Each comet has a greenish coma of expelled gas and an ion tail pointing
away from the Sun.

Growing Gallery: Comet SWAN25B
Tomorrow's picture: a third camera comet
__________________________________________________________________

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 September 30
A starfield is shown that has a bright comet. The comet shows a green
head on the lower left and an ion tail with significant structure
extending out to the upper right. Please see the explanation for more
detailed information.

Comet Lemmon Brightens
Image Credit & Copyright: Victor Sabet & Julien De Winter

Explanation: Comet Lemmon is brightening and moving into morning
northern skies. Besides Comet SWAN25B and Comet ATLAS, Comet C/2025 A6
(Lemmon) is now the third comet currently visible with binoculars and
on long camera exposures. Comet Lemmon was discovered early this year
and is still headed into the inner Solar System. The comet will round
the Sun on November 8, but first it will pass its nearest to the Earth
-- at about half the Earth-Sun distance -- on October 21. Although the
brightnesses of comets are notoriously hard to predict, optimistic
estimates have Comet Lemmon then becoming visible to the unaided eye.
The comet should be best seen in predawn skies until mid-October, when
it also becomes visible in evening skies. The featured image showing
the comet's split and rapidly changing ion tail was taken in Texas, USA
late last week.

Growing Gallery: Comet Lemmon in 2025
Tomorrow's picture: mopping up
__________________________________________________________________

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 October 1
A starfield is shown that has a multi-filament nebula flowing across it
horizontally. The most prominent colors are red and blue. Please see
the explanation for more detailed information.

NGC 6960: The Witch's Broom Nebula
Image Credit & Copyright: Brian Meyers

Explanation: Ten thousand years ago, before the dawn of recorded human
history, a new light would suddenly have appeared in the night sky and
faded after a few weeks. Today we know this light was from a supernova,
or exploding star, and record the expanding debris cloud as the Veil
Nebula, a supernova remnant. This sharp telescopic view is centered on
a western segment of the Veil Nebula cataloged as NGC 6960 but less
formally known as the Witch's Broom Nebula. Blasted out in the
cataclysmic explosion, an interstellar shock wave plows through space
sweeping up and exciting interstellar material. Imaged with narrow band
filters, the glowing filaments are like long ripples in a sheet seen
almost edge on, remarkably well separated into atomic hydrogen (red)
and oxygen (blue-green) gas. The complete supernova remnant lies about
1400 light-years away towards the constellation Cygnus. This Witch's
Broom actually spans about 35 light-years. The bright star in the frame
is 52 Cygni, visible with the unaided eye from a dark location but
unrelated to the ancient supernova remnant.

Tomorrow's picture: the shadowy realm
__________________________________________________________________

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)