Berachot 9b: Kestrel of the sun

In the Mishna on Berachot 9b, there is mention of sunrise. Thus:

מתני' מאימתי קורין את שמע בשחרית משיכיר בין תכלת ללבן ר' אליעזר אומר בין תכלת לכרתי (וגומרה) עד הנץ החמה ר' יהושע אומר עד שלש שעות שכן דרך מלכים לעמוד בשלש שעות הקורא מכאן ואילך לא הפסיד כאדם הקורא בתורה:

MISHNAH. FROM WHAT TIME MAY ONE RECITE THE SHEMA IN THE MORNING? FROM THE TIME THAT ONE CAN DISTINGUISH BETWEEN BLUE AND WHITE. R. ELIEZER SAYS: BETWEEN BLUE AND GREEN. AND HE HAS TIME TO FINISH UNTIL SUNRISE. R. JOSHUA SAYS: UNTIL THE THIRD HOUR OF THE DAY, FOR SUCH IS THE CUSTOM OF KINGS, TO RISE AT THE THIRD HOUR. IF ONE RECITES THE SHEMA' LATER HE LOSES NOTHING, BEING LIKE ONE WHO READS IN THE TORAH.

This is commonly called netz hachama. However, here is an image of a netz hachama.

Kestrel of the sun, netz hachama

(Netz is a hawk, a kestrel, a harrier, etc.; you get the idea.)

And this is an image of the hanetz hachama:

Sunrise, hanetz hachama

Indeed, the ha prefix of hanetz hachama is not the heh of the definite article. See for comparison Shir HaShirim 7:13:

יג  נַשְׁכִּימָה, לַכְּרָמִים--נִרְאֶה אִם-פָּרְחָה הַגֶּפֶן פִּתַּח הַסְּמָדַר, הֵנֵצוּ הָרִמּוֹנִים; שָׁם אֶתֵּן אֶת-דֹּדַי, לָךְ.

13 Let us get up early to the vineyards; let us see whether the vine hath budded, whether the vine-blossom be opened, and the pomegranates be in flower; there will I give thee my love.

See also this Wikipedia article.